1. Field of the Invention
The present invention relates to a linear-beam microwave tube, and more in particular, to a collector structure of the linear-beam microwave tube.
2. Description of the Related Prior Art
A linear-beam microwave tube for high power has a collector core for collecting electrons of electron beams, which turns into high temperatures and high voltages during its operation. Hence, the collector core comprises a cylindrical insulator made of ceramic around an outer peripheral portion thereof, and comprises further a radiator for heat sink around an outer peripheral portion of the insulator. FIG. 1A is a longitudinal sectional view of a conventional linear-beam microwave tube, and FIG. 1B is a transverse sectional view cut along the line Bxe2x80x94B of FIG. 1A. A collector section 1 is connected to a high frequency circuit portion 2, which guides electron beams emitted from a beam emission source (not shown), and comprises a collector core 4 for collecting electrons of electron beams and a vacuum holding insulator 5 for holding a vacuum state inside the collector section 1. The cylindrical insulator 6 made of ceramic is arranged by adhering on the outer peripheral portion of the cylindrical portion of the collector core 4, and, further, the cylindrical radiator 7 made of metal is arranged by adhering on the insulator 6. The collector section 1 transmits the heat generated by the collector core 4 to the radiator through the insulator 6 made of ceramic. However, though the ceramic material is a good material to boost a withstand voltage, a heat conductivity thereof is small comparing to metal. Therefore, the heat generated by the collector core 4 is not necessarily transmitted efficiently to the radiator 7.
Japanese Patent Laid-Opened No. 7-045207 discloses a collector core comprising an insulator made of ceramic in which a slit is formed so as to enhance radiation effect. While, in the case of a conventional collector core shown in FIG. 2, the insulator 6 and the radiator 7 comprise the slit, respectively. It is, therefore, possible for the collector core 4 to radiate the generated heat directly outside, and the radiation effect of the collector core 4 can be enhanced much more. However, the collector core of the microwave tube is usually formed by metal such as, for example, copper, and the radiator is also formed by metal, and consequently, an electric discharge tends to develop between the collector core and the radiator with a result that a withstanding voltage characteristic is deteriorated.
The present invention has been made in view of the foregoing disadvantages of the prior art.
Accordingly, it is an object of the present invention to provide a microwave tube having a collector core, which comprises high withstand voltage and high radiation characteristics.
The linear-beam microwave tube according to the present invention comprises a collector core, an insulator and a radiator. The insulator is arranged on an outer peripheral portion of the collector core and comprises a slit. Also, the radiator is arranged on an outer peripheral portion of the insulator, and comprises a slit on the portion corresponding to the above-described slit. The collector core is cut off at a portion, which corresponds to these two slits.
In one preferred embodiment of the present invention, the cut-off portion of the collector core is flat.
In another preferred embodiment of the present invention, the cut-off portion of the collector core is concave.